I've arrived at the pump before in the wife's car and not remembered which side it was on, but never moved it to correct my 'guess' and still be wrong.
I did however once, the day we collected a new car for the missus, had to ask an owner of the same car on the forecourt how the hell you opened the filler cap. Turned out there was a small button you press in the driver's door, low down, more or less next to your hip when closed. Never thought to look there.
